LITTLE ROCK (CNN) — U.S. Senator Mark Pryor and his new Republican challenger, Rep. Tom Cotton, are already aggressively going after each other 15 months before Arkansas voters go to the polls.

Announcing his candidacy August 6, Cotton repeatedly tied Pryor to President Barack Obama, who is deeply unpopular in the Natural State.

U.S. Represenative Tom Cotton

“Mark’s been running for office for almost 25 years. Every time, he says Arkansas comes first,” Cotton told a crowd of supporters at a kickoff barbecue in his hometown of Dardanelle in the Arkansas River Valley west of Little Rock. “It’s not so. Over the last 4 ½ years, for Mark Pryor, Barack Obama comes first.”

“Do you agree with Barack Obama 90 percent of the time? If so, Mark Pryor is your man. If not, stand with me.”

But on the same day Cotton announced, Pryor went up with a new TV ad painting Cotton as an extreme right winger, rather than a mainstream Arkansas conservative.

“Tom Cotton should be running — not for higher office but from his own record,” a soothing female voice intones after ripping Cotton for his votes against the farm bill, reduced interest rates on student loans and the Violence Against Women Act.

Pryor’s ad also accuses Cotton of “blind ambition” — a not-so-subtle reference to the congressman’s decision to seek higher office just seven months after his election to the House.

Cotton alluded to his political ambitions in his announcement statement, noting that “some people say I’m a young man in a hurry.”

A graduate of Harvard Law School who served tours in Iraq and Afghanistan as a captain in the U.S. Army, Cotton, 36, returned to Arkansas in 2012 to seek the 4th District congressional seat, which takes in rural areas south, west and northwest of metro Little Rock.

With funding from the Club for Growth and other national conservative groups, he easily won the seat, taking almost 60 percent of the vote in the general election.

U.S. Senator Mark Pryor

Pryor, 50, is scion of a prominent Arkansas political family. His father, David Pryor, served as governor and spent 18 years in the Senate before retiring in 1979.

Six years ago, Republicans didn’t even field a candidate against Pryor. But this time around, the GOP smells blood in the water, particularly because of Pryor’s deciding vote in favor of Obamacare in 2009.

However, Pryor has broken with Obama and the left wing of his party on a number of issues that are likely to help his re-election effort back home. His is just one of four Senate Democrats who still oppose same-sex marriage and also voted against a bill that would have expanded background checks for gun purchases.

In 2012, Obama lost Arkansas to Mitt Romney by nearly 24 points. In addition to Arkansas, Senate races in two other Southern states, Louisiana and North Carolina, feature Senate races in 2014 where Democratic incumbents are running in states Obama lost.

In a sign of how contentious the Arkansas Senate race will be, outside groups have already dumped more than $1 million into ads.